Known clutch torque controls exhibit certain disadvantages and among these disadvantages is the application to a fastener of undesired dynamic torque output which is different from that preset for a given job. Such results are obtained frequently in connection with known fastener setting power tools utilizing clutch mechanisms, many of which are provided with spring and cam arrangements and which feature sliding friction on torque transmitting components.
More specifically, a typical prior art clutch is schematically illustrated in FIG. 1A wherein a rolling element, specifically ball B, is forced against a clutch surface C by a flat upper clutch surface D. Ball B is pushed over cam E by a flat driving element F. As ball B moves over cam E, the clutch disengages and triggers a mechanism, not shown. Both the flat upper clutch surface D and the flat driving element F slide relative to ball B. This sliding action results in dynamic frictional loading which eventually is likely to cause undesired inconsistency and wear in a rotary power tool were the clutch incorporated in such a tool.
Such sliding friction on the torque transmitting components may in fact change the torque actually being transmitted because sliding action translates into dynamic friction in contrast to rolling friction. Rolling friction between relatively movable parts is much more consistent because such component parts do not slide relative to one another, particularly when maximum torque is being transmitted such as by relatively moving clutch parts.